Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on [email protected] for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact [email protected]

Cold Spell Prospects and Discussion (January + Early Feb 2012)

  • 04-01-2012 12:27pm
    #1
    Closed Accounts Posts: 2,667 ✭✭✭


    Please note that this is an outlook based on two successive runs and increasing evidence that a northerly/north-easterly outbreak is indicated around or in the days following 15 January. It is not a guarantee that colder weather will occur post mid-January, although confidence is growing in relation to such an eventuality.

    As indicated elsewhere on this forum, with signs increasing that we could soon see both a displacement and split of the polar vortex we are likely to see models increasingly signal wintry weather, most likely from an Arctic source initially. MT also alluded to this today.

    At present it looks like there will be a rise in high pressure to our west and northwest allowing Arctic air to sink south or southwestwards over Ireland and the UK around or just after mid-January i.e. 15-17th Jan. The exact positioning of these highs is not yet written in stone but the aforementioned represents the most likely scenario at this early stage.

    Based on current output, daytime temperatures would sink to low single figures. The cold spell could last for quite some time (at least 4-5 days) if high pressure continues to build over Scandinavia and Greenland as the models are presently indicating.

    Backedge snow would be likely almost everywhere as the cold front sweeps south across Ireland as the transition begins around the 16-18th. Wintry showers would follow for N, NW and E of the country in particular with some making their way into the Midlands and to the southeast. Elsewhere, it will be dry, bright and sunny with severe overnight air and ground frosts. Temperatures may be a few degrees in the extreme nw and sw as high pressure to our w and nw might result in a slack sw flow.

    What beyonds this period remains unclear although there are tentative signs that the weather will briefly become a little less cold before a more continental source of cold air extends over at least the eastern UK.

    In the meantime (next 10-12 days), the jetstream remains in control of our weather up to then. It will turn drier over the weekend but it will be wetter at times again next week. Temperatures will be slightly above average for the time of year as a whole over the next 10 days.

    (Below) Some charts indicating the change on the cards for the post mid-Jan period. These charts will upgrade and downgrade dramatically over the next few days but there will be general trend toward such a setup in the mid Jan period, most likely around 16-18th.
    JET STREAM SHIFT
    187123.png

    High pressure blocking
    187124.png

    Cold 850hpas
    187125.png


«13456758

Comments

  • Registered Users Posts: 767 ✭✭✭davidsr20


    Fingers crossed this comes off :)


  • Registered Users Posts: 845 ✭✭✭tylercollins


    Same date MArk Vogan is going for as well!



  • Closed Accounts Posts: 2,667 ✭✭✭WolfeIRE


    Same date MArk Vogan is going for as well!

    Thought his date was mid-December 2011?:p


  • Moderators, Technology & Internet Moderators Posts: 17,129 Mod ✭✭✭✭cherryghost


    Noice. ECM shows the potential of this occuring a bit earlier too. Fingers crossed it is then!

    I clicked on the thread without spotting the user who started it, completely assumed it was darkman's :P Well played, wolf, well played.


  • Registered Users Posts: 20,322 ✭✭✭✭Rikand


    so this is why M.T chose cla-15 for his forecast comp ;)


  • Advertisement
  • Registered Users Posts: 845 ✭✭✭tylercollins


    WolfeIRE wrote: »
    Thought his date was mid-December 2011?:p

    He has said alot of dates :P But his video this month is the same yours. Maybe he just likes the date of the 15th :D


  • Registered Users Posts: 2,855 ✭✭✭Nabber


    GEFS the only one running with this?
    Can't see anything similar on other models


  • Closed Accounts Posts: 2,667 ✭✭✭WolfeIRE


    Nabber wrote: »
    GEFS the only one running with this?
    Can't see anything similar on other models
    Because most other models do not go beyond 144-240hrs. However, height rises and movement favourable to the setup suggested by the GEFS are occuring in the latter stages of the ECMWF.

    Forgot to post these, by the way. Have not seen this downward trend all winter.

    187127.png

    187128.gif


    AO doesn;t need to go negative for a blast from the north to affect us but it certainly would help any sustained cold from developing. At least it is trending toward negative in the lead up to mid Jan
    187129.gif


  • Registered Users Posts: 2,655 ✭✭✭delw


    nice to finally see -8's in the 850hpa even if it is subject to change


  • Registered Users Posts: 1,789 ✭✭✭BEASTERLY


    But is the control run is at a lower resolution and less accuarate than the operational? Plus it is an outlier, i think the operational run will be what actually happens, i.e. what we have now!


  • Advertisement
  • Closed Accounts Posts: 2,667 ✭✭✭WolfeIRE




    Simon Keeling foresees a colder second half of January.


  • Registered Users Posts: 1,461 ✭✭✭Musicman2000


    BEASTERLY wrote: »
    But is the control run is at a lower resolution and less accuarate than the operational? Plus it is an outlier, i think the operational run will be what actually happens, i.e. what we have now!

    The operational will flip and flop over the next few days, as M.T has said, so what will happen is very hard to know yet


  • Registered Users Posts: 5,564 ✭✭✭Pangea


    Thanks for the information, what is 'Backedge' snow?


  • Registered Users Posts: 1,461 ✭✭✭Musicman2000


    Pangea wrote: »
    Thanks for the information, what is 'Backedge' snow?

    Colder air digging in behind a front crossing the country.


  • Closed Accounts Posts: 2,667 ✭✭✭WolfeIRE


    Pangea wrote: »
    Thanks for the information, what is 'Backedge' snow?

    Rain turning to snow as colder air pushes in behind the cold front. I think we saw a similar situation when the cold arrived in late Nov 2010.


  • Closed Accounts Posts: 2,667 ✭✭✭WolfeIRE


    BEASTERLY wrote: »
    But is the control run is at a lower resolution and less accuarate than the operational? Plus it is an outlier, i think the operational run will be what actually happens, i.e. what we have now!

    You're right Beasterly. But you should start seeing over the next few days a gradul trending toward what the operational is hinting at right now i.e. colder weather around mid Jan. If you get what I mean :(:confused::pac:

    I can't speculate about the severity or longevity of any cold weather later this month i.e. repeat of 2009 or 2010 etc.

    All I can comment on is the trends that are showing up a potential northerly blast around mid month. By the end of the month, this thread may indeed be turned on it's head.


  • Closed Accounts Posts: 469 ✭✭blackius


    *dons the unpopular hat*

    For newbie model watchers,those that started around november last year or the previous january,be very carefull here.

    There is every reason to be hopefull that a set of circumstances being discussed here and elsewhere may pan out to an eventual snowfest but the opposite could also happen.

    I've seen model agreement on snow and artic mageddon reaching our shores right up to t96 and then the whole thing back fires and doesn't happen at all with the cold instead sliding down the north sea somewhere or into SE europe.

    Have a look at the charts for early january 2007 [there will be threads here] for one of the best examples of a disaster like that.

    Thats why hoping and getting hopes up on FI charts is dangerous.

    Please couple your excitement about them with the risk that they might never happen.


  • Registered Users Posts: 1,461 ✭✭✭Musicman2000


    blackius wrote: »
    *dons the unpopular hat*

    For newbie model watchers,those that started around november last year or the previous january,be very carefull here.

    There is every reason to be hopefull that a set of circumstances being discussed here and elsewhere may pan out to an eventual snowfest but the opposite could also happen.

    I've seen model agreement on snow and artic mageddon reaching our shores right up to t96 and then the whole thing back fires and doesn't happen at all with the cold instead sliding down the north sea somewhere or into SE europe.

    Have a look at the charts for early january 2007 [there will be threads here] for one of the best examples of a disaster like that.

    Thats why hoping and getting hopes up on FI charts is dangerous.

    Please couple your excitement about them with the risk that they might never happen.

    Very wise words, and the GFS 12z dosent want to let go of its zonal setup, lets see what the ECM throws at us


  • Moderators, Science, Health & Environment Moderators Posts: 7,144 Mod ✭✭✭✭pistolpetes11


    Very wise words, and the GFS 12z dosent want to let go of its zonal setup, lets see what the ECM throws at us

    Joe Bastardi @BigJoeBastardi 2m Reply Retweet Favorite · Open
    The 12z GFS run and the worship of it baffles me, The GFS operational stinks in changing patterns and has wild swings


  • Closed Accounts Posts: 2,667 ✭✭✭WolfeIRE


    blackius wrote: »
    *dons the unpopular hat*

    You are spot on Black but I think most people here already realise that, myself included. The OP was pragmatic (use of the word possible in the thread) and based on all available data. I think those who visit the forum are more than aware of the ups and downs of models as the recent storm watching episodes have shown.

    As it transpires, the GFS 12z does show a northerly-northwesterly around 14-15th. But as Musicman says, the zonal setup remains more or less in charge. This is all FI and subject to change but models will chop and change considerably over the next few days.

    6034073


  • Advertisement
  • Registered Users Posts: 2,855 ✭✭✭Nabber


    WolfeIRE wrote: »
    Because most other models do not go beyond 144-240hrs.

    But the ones that do show a different story

    It's more of an FI chart. It is a long way out:cool: Maybe next week the models will all be singing the same tune. But we could end up with another JAN-FEB 2011 were the charts were great bbut the out come was not half as good.

    It would be nice to see a break in these Westerly set ups.

    CMC ENS
    12012000_0400.gif
    GFS
    12012012_0412.gif


  • Closed Accounts Posts: 3,548 ✭✭✭Harps


    GFS Control run has been encouraging for the past few days but still not a huge amount of support, the Op run again doesn't do much and ensemble support is limited albeit showing a downward trend. ECMWF has had a few hints at a change but just going for a brief toppler this morning. I wouldn't get too excited unless something starts to show up inside 192h

    An interesting prospect though considering there wasn't even been as much as a hint at a change from raging zonality all through December


  • Closed Accounts Posts: 2,667 ✭✭✭WolfeIRE


    Joe Bastardi has been twittering in the last hour. He can be followed here.

    top left euro 10 day..bottom left, verification top right GFS bottom rt verification. US model typical error pic.twitter.com/0CViEFuQ

    Change of source region, and trough east of Hawaii means widespread cold should hit and hold later next week and beyond

    GFS ensembles coming in and are continuing to go the way we have been describing. This is NOT Jan 06. there is a flip coming ( imo)

    In fact, I dont trust how cold the long term ensemble looks because its as if God asked me to draw the map.. ( ha ha). It is catching on

    Been warning clients for a week now about the way we flipped in the winter of 07.. warm through mid Jan, then the walls came down

    1984 had warm December, then Jan 1985 turned cold, 1st 2 weeks of Jan 1999 had top 5 cold, snowy pattern Chicago after warm Dec


  • Closed Accounts Posts: 2,693 ✭✭✭Redsunset


    Ha yeah just read it on Twitter. Very U.S focused however like he points out these have on knock on effects for Europe in the past


  • Closed Accounts Posts: 469 ✭✭blackius


    @nabber
    Looking at anything beyond 5 days in modeling is subject to so many increasing errors it cannot be trusted.

    I know theres a strong school of thought that you look into FI for trends and I like that but it's not to be trusted untill at the very least it comes inside 144hrs
    Then we can start tingling a tad...just a tad!


  • Closed Accounts Posts: 3,548 ✭✭✭Harps


    Very interesting ECMWF run with Greenland looking good again for something more than a toppler

    ECM1-240_dui7.GIF


  • Registered Users Posts: 1,461 ✭✭✭Musicman2000


    Harps wrote: »
    Very interesting ECMWF run with Greenland looking good again for something more than a toppler

    ECM1-240_dui7.GIF

    More thank likely out of that chart would be a northerly toppler for a few days, but still not to bad and hopefully the ECM will keep this trend on the next few runs.


  • Registered Users Posts: 1,789 ✭✭✭BEASTERLY


    More thank likely out of that chart would be a northerly toppler for a few days, but still not to bad and hopefully the ECM will keep this trend on the next few runs.

    I disagree, we havn't seen a high linking the Atlantic and Greenland in any of the northerly topplers. That high to me looks like it wont just crumble in the way of the next low. And this is the ECM at 240 hrs! I'm slowly getting less skeptical, let's see what the 18z GFS brings.


  • Moderators, Motoring & Transport Moderators Posts: 6,520 Mod ✭✭✭✭Irish Steve


    Harps wrote: »
    Very interesting ECMWF run with Greenland looking good again for something more than a toppler

    At the risk of raining, or even snowing on your parade, the issue will be what happens in the period following, if this even happens, if the warm sector comes through too soon, we might get a hammering, and then massive flooding behind it as it all thaws off in the rain, and I've seen that before in the UK, it ended up getting me a very good job managing a large IT installation after a flood wiped out all the old accounting machines, and the company had to move very rapidly to upgrade to a new system, and that was the start of the story that brought me to Ireland, but that's thread drift.

    That winter, we had 6" of snow, and then 2 days later, the warm sector rattled through and threw significant rain at the snow, and the whole lot came rattling off the moors in a big hurry, and couldn't get through all the bridges and the like, so local flooding. Can't remember if it was 83 or 84 now, and a quick search didn't give me what I needed, but it was a wild few days.

    Shore, if it was easy, everybody would be doin it.😁



  • Advertisement
  • Closed Accounts Posts: 2,667 ✭✭✭WolfeIRE


    The FI end of the 12z ECM is encouraging if you like cold weather. Second time in a row that the 12Z has delivered significant potential for break in the longstanding zonal setup.

    The building blocks are falling into place although, as Blackius has pointed out, they can come tumbling back down just as easy.

    At least we are now been given something to discuss in terms of the possibility of 'cold' winter weather and an end to the jetstream driven weather of the past month or more. No offence to those who like the stormy weather that we have been experiencing.

    By the way, much drier and calmer weather looks like kicking in for the weekend for all but the far west and north (as usual).

    ECH1-240.GIF?04-0


    NAO and AO remain on a fine line between indicating a colder spell and more of the same.

    187171.gif


This discussion has been closed.
Advertisement